As is known, light emitting diodes (LEDs) are devices that generate light when current/voltage is applied to the device. LED light output is proportional to the LED current, and thus, a current source is generally used to drive the LEDs for a given application. LEDs can be used in any number of applications (e.g., automotive headlamps, residential and commercial lighting, optoelectronics circuitry, and manufacturing processes), and provide a number of benefits such as long operation life, high efficiency and low profile, relative to other lighting technologies.
In many applications, an array of LEDs is provided where the array includes a plurality of LED strings connected in parallel, where each string includes a number of serially connected LEDs. Due to the wide unit-to-unit variation of LED forward voltage, parallel LED strings require a current limiter or other current regulator in series with each string to force current sharing amongst the strings. For instance, resistors are commonly used as current limiters. However, there are a number of non-trivial limitations associated with such current sharing techniques.